ISO/FDIS 5013

FINAL DRAFT
International
Standard
ISO/TC 33
Refractory products —
Secretariat: BSI
Determination of modulus of
Voting begins on:
rupture at elevated temperatures
2026-09-21
Produits réfractaires — Détermination du module de rupture par
Voting terminates on:
flexion à températures élevées
2026-11-16
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 33
Refractory products —
Secretariat: BSI
Determination of modulus of
Voting begins on:
rupture at elevated temperatures
Produits réfractaires — Détermination du module de rupture par
Voting terminates on:
flexion à températures élevées
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Number, shape, size and preparation of test pieces . 4
6.1 Number of test pieces .4
6.2 Shape and size .4
6.3 Preparation .5
7 Procedure . 6
7.1 Measuring test pieces, checking test jig, positioning test piece .6
7.2 Heating.6
7.3 Loading .6
8 Expression of results . 7
9 Test report . 7
Annex A (normative) Measurement of temperature distribution in the test piece . 9
Annex B (informative) Precision and bias . 10
Bibliography .13

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 33, Refractories.
This second edition cancels and replaces the first edition (ISO 5013:1985), which has been technically
revised.
The main changes are as follows:
— revised definitions;
— recommendation for lower HMOR values change to a stress rate of 0,05 MPa/s;
— addition of an informative annex on precision and bias and comparison of different test methods for
C-containing materials.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
FINAL DRAFT International Standard ISO/FDIS 5013:2026(en)
Refractory products — Determination of modulus of rupture
at elevated temperatures
1 Scope
This document specifies a method for the determination of the modulus of rupture of dense and insulating
shaped refractory products at elevated temperatures, under conditions of a constant rate of increase of
stress.
NOTE A method for determination of the modulus of rupture at ambient temperature is given in ISO 5014.
Shaped refractories are those which have fixed geometry and dimensions when delivered to the user. This
document is applicable to standard shape refractory bricks, but also special shapes of refractory products
and pre-cast products. This document is also applicable to unshaped refractories (see ISO 1927-6) after
preparation of test specimens according to ISO 1927-5.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 1893, Refractory products — Determination of refractoriness under load — Differential method with rising
temperature
ISO 13385-1, Geometrical product specifications (GPS) — Dimensional measuring equipment — Part 1: Design
and metrological characteristics of callipers
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
modulus of rupture
MOR
σ
F
maximum stress that a prismatic test piece of specified dimensions can withstand when it is bent in a three-
point bending device
3.2
test temperature
temperature at the mid-point of the tensile face of the test piece

3.3
three-point bending
means of bending a beam test piece whereby the test piece is supported on bearings near its ends, and a
central force is applied
3.4
dense shaped refractory product
product with specific dimensions, having a true porosity of less than 45 % by volume, when measured in
accordance with ISO 5017
3.5
shaped insulating refractory
shaped refractory having a true porosity of not less than 45 % by volume, when measured in accordance
with ISO 5016
3.6
sample
representative collection of items that can be obtained by sampling according to a sampling plan agreed
upon by the interested parties
Note 1 to entry: An example of applicable sampling plan is given in ISO 5022.
3.7
item
refractory brick or shape
3.8
test piece
test specimen
piece of material extracted from an item (3.7) and suitably shaped and prepared for the test
4 Principle
Test pieces taken from items (bricks) are heated to the test temperature under controlled atmosphere. After
being maintained at this temperature until a uniform temperature is reached, the test pieces are loaded at a
constant rate of increase of tensile stress until failure occurs.
5 Apparatus
5.1 Test jig
The loading device shall have two bearing edges to support the test piece and one for the application of the
load. The three bearing edges shall be parallel to each other. For normal test pieces, the distance between the
bearing edges supporting the test piece shall be 125 mm ± 2 mm, with proportionate separations for other
test piece lengths (see 6.2). The loading bearing edge shall be placed centrally between the two supporting
bearing edges with an accuracy of ±2 mm (see the figure 1).
The bearing edges and test pieces shall be free from any reaction on contact at the test temperature.
The bearing edges shall have a length not less than 5 mm greater than the width of the test pieces and a
radius of curvature of 5 mm ± 1 mm.
Since the bearing edges become flattened with use, they shall be examined periodically to ensure that their
radii remain within these limits.
The distance between the two supporting bearing edges (see the figure) shall be measured at room
temperature to an accuracy of ±0,5 mm (this value is used in the calculation of the modulus of rupture).

5.2 Testing machine
Capable of applying a force uniformly to the loading roller in order to stress the test piece. The machine
shall be capable of applying this force at a constant loading rate. The test machine shall be equipped for
recording the peak load applied to the test piece. The accuracy of the test machine shall be in accordance
with ISO 7500-1, Grade 2 (accuracy 2 % of indicated load), or better.
5.3 Furnace
5.3.1 The furnace shall be one of the following types:
a) batch type, in which a number of test pieces are heated to the test temperature together and tested in
turn;
b) sequential type, in which the test pieces are heated to the test temperature one after another as they
pass through the apparatus.
5.3.2 ln either case, the furnace shall be capable of providing the overall heating of both the test jig and the
test pieces, and shall be so designed that at the moment of test, the temperature distribution in the test piece
is uniform within ±10 °C.
5.3.3 The atmosphere in the furnace shall be one of the following, as agreed between the parties
concerned in the test: air, some other specified gas, or the specimen shall be covered with graphite (or fine
metallurgical coke) in a box with a lid.
5.4 Temperature measuring device
5.4.1 The test temperature (3.2) shall be measured by a calibrated thermocouple placed at a maximal
distance of 20 mm from the midpoint of the tensile face of the test piece.
5.4.2 The relationship between this test temperature and the furnace temperature shall first be
established and shall be checked periodically in accordance with the procedure set out in Annex A.
5.4.3 During the test, the furnace shall be maintained at such a temperature that the midpoint of the
tensile face of the test piece is nominally at the required test temperature.
5.5 Drying oven, capable of being controlled at (110 ± 5) °C, or other device which has an equivalent
heating effect.
For MgO-containing products, it is recommended to dry the test pieces to constant mass at (150 ± 10) °C.
NOTE A fan-assisted oven with ventilation and an exhaust air damper would assist in attaining an even
temperature distribution and efficient drying of the test pieces.
5.6 Calliper, which shall be in accordance with ISO 13385-1, of resolution 0,1 mm, or alternative calibrated
device measuring to this resolution, for measurement of test piece dimensions.

Key
1 loading bearing edge
2 compression face
3 supporting bearing edges
4 tensile face (not an original face of the item)
L span, distance between the points of support of the test piece
s
h height of the test piece
Figure 1 — Arrangements and dimensions of test piece and bearing edges of the test jig; for
tolerances, see Table 1
6 Number, shape, size and preparation of test pieces
6.1 Number of test pieces
6.1.1 A sample consists of at least four items, obtained by sampling according to a sampling plan agreed
upon by the interested parties, e.g. ISO 5022.
6.1.2 The number of test pieces to be tested for each item (brick) at each test temperature shall be agreed
between the interested parties and shall be the same for each item; it shall be stated in the test report.
If only one item is available, whenever possible, at least four test pieces will be taken in order to compose a
representative sample.
6.2 Shape and size
6.2.1 Unless otherwise agreed, the test piece shall be a rectangular bar with a cross-section of
25 mm ± 1 mm x 25 mm ± 1 mm and a length of about 150 mm. The longitudinal faces of each test piece shall
be parallel to each other within a tolerance of ±0,2 mm and the si
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